This section will be broken into two parts. In the first part, we will review the original definition of a 4-manifold trisection given by Gay and Kirby in [1]}. We elaborate slightly on the definition by giving an equivalent definition involving 3-dimensional compression bodies as well as by including a description of the induced decomposition of the boundary in the relative case. This elaboration will assist in our exposition of \(\star \) -trisections. We formally introduce \(\star \) -trisections in the second part of this section.
